Link to API/docs is dead

[philippw]

Description

The link on the README.md page to the documentation on webcomponents.org is dead.

Expected outcome

Link to the relevant webcomponents.org page

Actual outcome

404 not found with a reference to the iron-a11y-keys-behavior

Live Demo

Steps to reproduce

Click the link at the top

Browsers Affected

• [x] Chrome
• [x] Firefox
• [x] Safari 9
• [x] Safari 8
• [x] Safari 7
• [x] Edge
• [x] IE 11
• [x] IE 10

[philippw]

Has been resolved in webcomponents.org/webcomponents.org#1073.